This proposal is designed to expand our knowledge of the in vivo function of adhesion receptors in vascular injury. The project will focus on graft injury following xenogeneic organ transplantation as a model for leukocyte-mediated vascular damage. The primary focus of this project will be identify the adhesion receptors that serve as mediators of human leukocyte attachment to porcine endothelium with particular attention directed towards the selectin family of adhesion receptors. Since this family of receptors, L-, E-, and P-selectin and their corresponding ligands are well conserved during recent mammalian evolution, it is likely that they will serve a major role in the initial attachment of human leukocytes to epithelial cells. Initial studies will focus on the in vitro characterization of porcine endothelial cell cultures and the characterization of their responses to inflammatory cytokines and the kinetics of induction of known receptors and receptor ligands. Antibodies reactive with the various human and porcine adhesion receptor will be used to block leukocyte-endothelial interactions. Additional monoclonal antibody reagents reactive with porcine adhesion receptors will also be developed should they be required for these studies. Attachment mechanisms operable under both static and non-static conditions will be assessed. A second set of studies will be examine the induction of adhesion receptors by transplanted tissues in vivo during the various stages of organ rejection using PCR amplification analysis and immunohistochemistry. This information will provide a directed approach for the use of adhesion receptor targeted therapies for interfering with the rejection process. Monoclonal antibodies reactive with L-selectin are completely effective at ablating ischemia-reperfusion injury in other animal models. It is therefore likely that antibodies reactive with the selectins will provide useful therapeutics for preventing leukocyte infiltration how alterations in the endothelial lining regulate the attachment and entry of leukocytes into sites of inflammation should generate new and useful approaches for increasing the utility and survival of xenografts.